1. FIELD OF THE INVENTION
The present invention relates to a method and apparatus for solidifying radioactive waste by using a solidifying agent capable of sealing radioactive waste that has been processed to reduce its volume. In particular, the solidified radioactive nuclides present in the waste have a long half life, and after being solidified must be prevented from being released into the environment, such as into the ground water, by leaching.
2. DESCRIPTION OF RELATED ART
Concentrated radioactive liquid waste and radioactive resin slurry waste are produced in an atomic power plant. Conventionally, the radioactive waste, which typically has a 20 percent solids content, is solidified as it is with cement in a container to form a solidified radioactive waste. Recently, attempts have been made to solidify a concentrated liquid waste or slurry that has been dried to form a powder that is granulated or pelletized with cement Further, attempts are being made to solidify liquid wastes that have been concentrated into the form of a sludge by mixing the sludge with a solidifying agent in a container.
In Japan, a final disposal system for solidified radioactive wastes has been established. The plan, which is to by fully implemented in 1991, focuses on land as the area in which the radioactive waste will be finally disposed. The standards for implementing the plan are being prepared, and Table 1 shows one of the standards, Sub-section 3 of Section 13 of the Enforcement Ordinance on the Regulations of Nuclear source Material, Nuclear Fuel Material and Reactor (Section 324 of Government Ordinance, Nov. 21, 1957; amended on Mar. 17, 1987). The table shows the maximum allowable levels of radioactive concentration that are permitted for solidified radioactive wastes.
TABLE 1 ______________________________________ Wastes generated in Carbon 14 1 Ci/t facilities or plants Cobalt 60 300 Ci/t with reactor installed, Nickel 63 30 Ci/t and solidified in a Strontium 90 2 Ci/t container. Cesium 137 30 Ci/t Radioactive 0.03 Ci/t substance radiating .alpha. rays ______________________________________
In this table, the radioactive nuclide concentrations are regulated with respect to carbon 14 (hereinafter referred to as "C-14"), cobalt 60 (hereinafter referred to as "Co-60"), nickel 63 (hereinafter referred to as "Ni-63"), strontium 90 (hereinafter referred to as "Sr-90"), cesium 137 (hereinafter referred to as "Cs-137") and a substance radiating o radiation (hereinafter referred to as ".alpha. waste").
In the industry, there is a desire to concentrate the radioactive waste to its highest permitted level in order to reduce the space needed for the long term storage of the waste. As the radioactive concentration of the waste is increased, however, there exists a possibility that the amount of leaching of the solidified waste will also be increased. Therefore, many attempts are being made to solidify the radioactive waste as it is or after concentrated so that the amount of leaching for such a solidified waste does not exceed levels of leaching that are considered by the industry to be permissible.